Erosion

contrast positive and negative erosion

removal of soil or rock by water, wind, ice or gravity from on earth’s surface (negative) and deposition in another place (positive)

geological vs accelerated erosion

geological - takes place slowly and naturally (no influence from humans)

accelerated - due to human activity

______ erosion can be 10 000 times as destructive as _____ erosion

accelerated and geological

adverse effects of soil erosion

• reduces soil fertility

• soil degradation

• spread of nutrients, pathogens, pesticides… attached to soil particles

• increases turbidity of rivers and lakes = degrades fish habitat

two main types of soil erosion

water and wind

water erosion increases with slope ______

slope degree and length

_____ erosion has a low risk on the Prairies

water

are there signs of water erosion in albertan soil zones

yes

where are signs of water erosion most seen in alberta

landscapes with long steep slopes

what regions is soil erosion more important

semi arid and arid regions

water erosion is restricted to ______ land

sloping

_____ surfaces are susceptible to wind erosion

all soil surfaces

what land usually has higher soil wind erosion

level slopes if the surface is smooth and no vegetation

____ erosion is more important on the Prairies

wind

why is wind erosion a constant concern in the Prairies

dry climate and large cropped area

soils low in _____ are at higher risk of wind erosion

OM

does brown soil have a higher or lower risk of wind erosion

higher (has low OM)

why is wind erosion risk aggravated around Lethbridge

high speed chinook winds (dries the soil)

little snow cover during winter

what size of particles are the most susceptible to wind transport

0.1 to 0.5 mm (medium and fine sand)

_____ sized particles resist wind transport but can be moved in _______

particles up to 1.0mm (coarse and very coarse sand) but can move by high speed winds

what is important for evaluating wind erosion for coarse textured soils

knowing sand sub fraction amounts

does coarse sandy loam or very fine sandy loam have a higher soil erodibility factor

very fine sandy loam

three processes of wind erosion transport

creep, saltation, suspension

what is creep

rolling of aggregates and particles of about 1.0 mm on soil surface

creep fills in furrows which ______ surface roughness and _____ wind erosion risk

reduces and increases

what are the main particles for creep

coarse sand

what accounts for 5-25% of wind erosion

creep

what is saltation

movement of medium to fine sand by a series of short jumps

what are the ideal particles sizes for saltation

medium to fine sand or very small aggregates (0.1 to 0.5 mm)

how high are saltation jumps

within 30cm of surface

what accounts for 50 to 90% of soil movement

saltation

what is suspension

removal of soil particles less than 0.1 mm and OM as dust clouds

_______ soil movement greatly affects soil productivity

suspension

_____ soil movement can move particles several hundreds of km

suspension

what particle movement accounts for 15% of wind erosion

suspension

what are seven factors affecting wind erosion

1. wind velocity

2. soil texture

3. soil structure

4. SOM content

5. tillage

6. vegetation

7. summer fallow

what is summer fallow

practice of leaving farmland bare for an entire growing season while intensely tilling soil

_____ leaves soil at high risk of severe wind erosion

summer fallow

erosion is _____ under natural vegetation

minimum

what does erosion result in with bare soils

blow out

what two legumes has caused severe erosion risk on irrigated lands

potato and sugar beet

why have potatoes and sugar beets caused severe erosion risk

• complete topsoil disturbance

• very little cover left after harvest

what soil/texture are most affected by potato and sugar beet after harvest

brown soil zone (low SOM)

coarse textured soils

why does the Taber area have high erosion risk

large areas of sandy soils planted with potato and beets

what can excessive tillage cause

pulverize soils which increases risk of severe wind erosion

what tillage tool will severely increase wind erosion risk

moldboard plow

why are aggregates harder to move than soil particles

they are heavier

soils with more ____ are more resistant to wind erosion

OM

what is the benefit of SOM

helps hold aggregates together - less erosional risk

potential for wind erosion begins when wind speeds increases to _____ at the soil surface

25 km/h

______ textured soils have the greatest erosion risk

coarse textured (sandy loam, loamy sand, sand)

what are some methods of reducing wind erosion

• reduce tillage

• increase surface roughness

• avoid summer fallow

• wind barriers

• seed a cover crop

• biocrusts

• perennial forage

• apply manure

• increase vegetation cover

what is the ideal standing stubble for reducing wind erosion

12 in

value of residue cover depends on the amount of ______ and the rate of _____

crop residue and decay

what plants leave good residue cover and decay slowly

cereals

what plants decay very quickly and don’t give much soil protection

canola, pea, lentil. sunflower

_____ and ____ leave soil at highest risk of erosion

sugar beets and potatoes

examples of wind barriers

rows of straw bales

perennial grass

caragana (used as shelter beds)

what is a biocrust

soil crust formed by microbes

what method of reducing wind erosion should only be used as an emergency measure

increase surface roughness

what were the main reasons for erosion reduction in the prairies

adoption of no till and continuous cropping

severe wind erosion removed _____ horizon in some areas which was never replaced

A horizon

what event left unproductive fields and ruined crops

dust bowl